Golf club shaft

ABSTRACT

The aerodynamic performance of a golf club shaft is improved by texturing the outer surface of the hozzle end portion of the shaft shank to provide an arithmetic mean of profile roughness which is greater than about 0.50 microns. This profile roughness is significantly greater than the arithmetic mean of profile roughness of a conventional smooth surface of a golf club shaft, which is typically between about 0.47 microns and about 0.50 microns. A roughness average on the hozzle end portion of the shank of a golf club shaft of between about 4.3 microns and about 5.0 microns is preferable. The hozzle end portion having such an enhanced roughness average should extend at least about five centimeters and no greater than about fifty centimeters from the tip of the golf club shaft that is inserted into the club head hozzle. A golf club shaft having these features will create less wake turbulence and less wake vacuum in moving through the air during a golf swing than a conventional golf club shaft. This enhances the speed and control of movement of the golf club head during a golf swing.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an improved construction for a golf club shaft. The invention has particular applicability to golf clubs used to drive golf balls long distances, such as golf drivers.

[0003] 2. Description of the Prior Art

[0004] The shafts for golf clubs used to drive golf balls long distances have heretofore had a fairly standardized construction. The club shaft has an elongated shank of circular cross-sectional configuration. For many years golf club shafts were formed of wood and were of a solid construction, but modern shafts are now typically hollow and formed of metal alloys of aluminum, titanium, and other metals. The shafts for golf clubs used to drive golf balls long distances, such as drivers, mashies, and No. 3 and 4 wedges, are typically between about one hundred and one hundred twenty-five centimeters in length. The shaft decreases in diameter from an upper, butt end at which the grip is located to an opposite, lower hozzle end which terminates in a tip that is inserted into the hozzle of a golf club head. The maximum diameter of such a golf club shaft at the butt end is typically no greater than about 2.5 centimeters and the minimum diameter at the hozzle end is typically no smaller than about 0.7 centimeters.

[0005] In prior art golf club shafts it is known that the club shaft surface and outer surface structure is an integral part of the golf shaft and of the overall golf club. The accepted belief in golf club shaft design is that the outer surface of the shaft should be as smooth as possible so as to minimize air resistance as the shaft is swung through the air to drive a golf ball a long distance. The concept has been that a smooth outer surface of a golf club shaft, particularly the hozzle end portion of the shaft which moves at the maximum velocity, will facilitate airflow past the shaft surface. The goal in golf club shaft design is to produce a golf club shaft which generates the least possible air resistance in its movement, particularly movement at high velocity. To this end golf club shafts have typically been designed with as smooth an outer surface as possible without significant surface roughness or texture.

SUMMARY OF THE INVENTION

[0006] It is an object of the present invention to manipulate and reduces surface airflow and turbulence over a golf club shaft surface during the downswing phase of the golf swing at maximum velocity. This reduction in turbulent airflow by providing the golf club shaft with a roughened surface texture coating assists in the breakup of airflow and lessens the drag vacuum so that the golf club shaft and golf club head will travel faster and will be more stable during the down swing. This granulated surface texture coating improves the Reynolds numbers which are used by aeronautical engineers to show a measurement of air drag on an object.

[0007] The degree or extent of surface roughness of a golf club shaft using the “Ra” scale is measured in microns. Roughness readings on the “Ra” scale represent the arithmetical mean of all profile values. This measure of roughness is also known as “roughness average”. In determining roughness average according to the present invention data was collected using a Perthen profilometer.

[0008] Contrary to conventional wisdom, it has been discovered, according to the present invention, that a smooth outer surface on the golf club shaft produces greater air resistance and wake turbulence than a golf club shaft covered with a textured or granulated surface coating that exhibits a certain degree of roughness. Air turbulence is particularly reduced if the hozzle end portion of the golf club shaft is coated with a granulated coating.

[0009] In one broad aspect of the present invention may be considered to be an improvement in a golf club shaft which has a hozzle end terminating in a tip, an opposite butt end, and a shank that tapers from a smallest diameter at the hozzle end to a largest diameter at the butt end. According to the improvement of the invention the outer surface of the hozzle end of the shank has an arithmetic mean of profile roughness of greater than about 0.50 microns. Preferably the hozzle end of a golf club shaft, according to the invention, is no less than about five centimeters and no greater than about fifty centimeters in length and has an arithmetic mean of profile roughness of between about 4.3 microns and about 5.0 microns.

[0010] In another broad aspect the invention may be considered to be an improvement in a golf club shaft having a hozzle end and a tip adjacent thereto for insertion into a golf club hozzle. According to the improvement of the invention the hozzle end has an outer surface that is covered with a textured surface coating having an arithmetic mean of profile roughness of greater than 0.5 microns.

[0011] In still another aspect, the invention may be considered to be an improvement in a golf club shaft which has a hozzle end terminating in a tip, an opposite butt end, and a shank that tapers from a smallest diameter at the hozzle end to a largest diameter at the butt end. According to the improvement of the invention at least a portion of the outer surface of the shank has a granulated surface texture thereon defining peaks with valleys therebetween. The surface texture has an arithmetic mean of profile roughness, as measured between the peaks and valleys, of at least about 0.50 microns. The peaks may be considered to be the tips of the radial projections from any surface most distant from the longitudinal axis of the golf club shank, while the valleys may be considered to be the surfaces closest to the shank axis.

[0012] The golf club shaft shank may be considered to be divided along its length into several adjacent portions. A tip of a slightly reduced diameter projects from the hozzle end portion of the shaft shank. The shaft shank also has a lower intermediate portion located adjacent the hozzle end portion and an upper intermediate portion located longitudinally adjacent the lower intermediate portion. The lower intermediate portion of the shank is thereby located longitudinally between the hozzle end portion of the shank and the upper intermediate portion thereof. The upper intermediate portion of the shank is located longitudinally between the lower intermediate portion and the butt end of the shank.

[0013] The surface at the lower intermediate portion of the shank is preferably granulated with a surface texture having an arithmetic mean of profile roughness of about one-tenth that of the hozzle end portion. The surface of the upper intermediate portion of the shank is granulated with a surface texture having an arithmetic mean of profile roughness greater than that of the lower intermediate portion and less than that of the hozzle end portion. The surface of the shank is preferably granulated with an arithmetic mean of profile roughness of between about 4.3 microns and about 5.0 microns at the hozzle end, between about 0.43 microns and about 0.50 microns at the lower intermediate portion, and between about 0.80 microns and about 0.90 microns at the upper intermediate portion. The butt end portion of the shank is almost completely covered by a conventional thermoplastic rubber or leather grip. The upper or butt end portion of the golf club shaft shank is preferably smooth and is not coated at all and has a profile roughness of between about 0.47 microns and about 0.50 microns. Since this upper portion of the golf club shaft is covered by the structure of the grip, its surface texture is of no great importance.

[0014] The invention may be described with greater clarity and particularity by reference to the accompanying drawings.

DESCRIPTION OF THE DRAWINGS

[0015]FIG. 1 is a perspective view illustrating a golf club head and the lower portion of one embodiment of a golf club shaft according to the invention.

[0016]FIG. 2 is a front elevational view of a preferred embodiment of a golf club shaft according to the invention shown in isolation.

[0017]FIG. 3 is a rear elevational view of the golf club shaft shown in FIG. 2.

[0018]FIG. 4 is a diagram that graphically depicts the profile roughness of the surface of the golf club shaft shank along its length.

DESCRIPTION OF THE EMBODIMENT

[0019]FIG. 1 illustrates the lower portion of a golf club 10 which is a golf club driver. The driver 10 has a club head 12 mounted at the lower extremity of a golf club shaft 14. The club ahead 12 has a ball impact face 16, an upper surface 18, a toe 20, and a hozzle 22. The golf club driver 10 also includes a back face, a sole, and a heel which are not visible in FIG. 1. The hozzle 22 defines a cylindrical annular opening therewithin configured to receive the cylindrical tip 24 of the golf club shaft 14. The golf club shaft tip 24 extends into the hozzle 22 and is concealed from view in FIG. 1, but is visible in the drawing views of FIGS. 2 and 3 which show the golf club shaft 14 in isolation.

[0020] The golf club shaft 14 consists of a shank 26, a tip 24 extending from the lower extremity of the shank 26, and a golf club grip (not shown). The golf club shaft 14 is typically constructed of graphite which is conventional in the field of golf club shaft design. The golf club shaft 14 also has a length and diameter of conventional dimensions.

[0021] Although there are no pronounced cross-sectional delineations along its length, the shank 26 of the golf club shaft 14 may be considered to be divided into a plurality of longitudinally adjacent portions. Specifically, and as indicated in FIG. 4, the shank 26 may be considered to be delineated into a lower, hozzle end portion 30, a lower intermediate portion 32, an upper intermediate portion 34, and a butt end portion 36. These portions are all of gradually increasing diameter proceeding from the tip 24 at which the hozzle end portion 30 terminates, to the butt end portion 36. Each of the several portions of the golf club shaft shank 26 has a different uniform roughness average about its circumference, as illustrated in FIGS. 2 and 3. Each of the portions 30, 32, 34 and 36 is delineated from the next longitudinally adjacent portion by a change in roughness average on its surface, as indicated in FIG. 4.

[0022] The hozzle end portion 30 of the shank 26 is delineated and defined by the longitudinal length at which the lower extremity of the shank 26 is painted with a granulated, textured paint having a profile roughness of greater than about 0.50 microns. The profile roughness at the hozzle end portion 30 and adjacent the tip 24 is greater than about 0.5 microns and is preferably greater than one micron. The profile roughness elsewhere on the surface of the shank 26 is preferably less than one micron.

[0023] Preferably, the hozzle end portion 30 has an arithmetic mean of profile roughness of between about 4.3 microns and about 5.0 microns. The hozzle end portion 30 of the golf club shaft shank 26 shown in FIGS. 2 and 3 has a roughness average of about 4.5 microns. A paint having this surface texture when dry is applied along the hozzle end portion 30 which may vary in length from as little as about five centimeters from its demarcation with the unpainted tip 24 and about fifty centimeters therefrom. The preferred length of the hozzle end portion having a profile roughness of about 4.5 microns is between about twenty-two centimeters and about twenty-five centimeters.

[0024] The lower intermediate portion 32 of the golf club shaft shank 26 is located longitudinally adjacent to the hozzle end portion 30 and is also coated with a much more lightly textured or granulated paint. The paint that coats the lower intermediate portion 32 has an arithmetic mean of profile roughness which is about one-tenth that of the adjacent hozzle end portion 30. As indicated in FIG. 4, the surface texture profile roughness of the coating on the lower intermediate portion 32 is between about 0.43 microns and about 0.50 microns. The lower intermediate portion 32 of the golf club shaft shank 26 shown in FIGS. 2 and 3 has a roughness average of about 0.48 microns. The length along the shaft shank 26 at which this coating is applied and remains exposed defines the length of the lower intermediate portion 32. Preferably, the lower intermediate portion 32 is between about ten centimeters and about fifty centimeters in length.

[0025] The upper intermediate portion 34 which is longitudinally adjacent the lower intermediate portion 32 is preferably coated with a paint having an arithmetic mean of profile roughness greater than the paint covering the lower intermediate shank portion 32, but considerably less than the profile roughness at the hozzle end portion 30. The upper intermediate portion 34 of the shaft shank 26 is preferably between about ten centimeters and about fifty centimeters in length and has an outer surface coating having an arithmetic mean profile roughness of between about 0.80 microns and about 0.90 microns. The upper intermediate shank portion 34 of the golf club shaft shank 26 illustrated in FIGS. 2 and 3 has a roughness average of about 0.88 microns.

[0026] The butt end 36 of the shank 26 at the relatively large diameter upper end of the golf club shaft 14 opposite the tip 24 is typically not painted at all. This portion of the golf club shaft 14 is normally covered almost entirely with a thermoplastic rubber, rubber, plastic, or leather grip and is typically between about fifteen centimeters and about forty centimeters in length. The outer surface of the unpainted butt end portion of the shank 26 typically has an arithmetic mean of profile roughness of between about 0.47 microns and about 0.50 microns. The roughness average of the butt end portion 36 of the golf club shaft shank 26 depicted in FIGS. 2 and 3 is about 0.48 microns. However its surface texture is of no great consequence since it is covered by the golf club grip.

[0027] When the golf club driver 10 is swung to hit a golf ball, the golf club shaft 14 moves more smoothly through the air and creates less wake turbulence and vacuum than a conventional golf club shaft. As a consequence, the club head 12 will move with a greater speed and under more accurate control as contrasted with the movement of the head of a conventional golf club swung in the same stroke. The modification of the surface texture roughness of the several portions of the golf club shaft 24 thereby improves the power and accuracy of a golfer's driving game.

[0028] Undoubtedly, numerous variations and modifications of the invention will become readily apparent to those familiar with the construction and design of golf clubs. For example, while the roughness average ranges described with respect to the embodiment of the golf club 10 are preferred, a considerable deviation from these values is possible. A golf club shaft constructed according to the present invention will provide beneficial results as long as the profile roughness of the hozzle end portion is greater than about 0.50 microns. Accordingly, the scope of the invention should not be construed as limited to this specific embodiment depicted and described, but rather is defined in the claims appended hereto. 

I claim:
 1. In a golf club shaft which has a hozzle end terminating in a tip, an opposite butt end, and a shank that tapers from a smallest diameter at said hozzle end to a largest diameter at said but end, the improvement wherein the outer surface of said hozzle end of said shank has an arithmetic mean of profile roughness of greater than about 0.50 microns.
 2. A golf club shaft according to claim 1 further characterized in that said hozzle end of said shank is no less than about five centimeters and no greater than about fifty centimeters in length and has an arithmetic mean of profile roughness of between about 4.3 microns and about 5.0 microns.
 3. A golf club shaft according to claim 2 wherein said shank has a lower intermediate portion located longitudinally adjacent said hozzle end and an upper intermediate portion longitudinally adjacent said butt end and said intermediate portions are located longitudinally adjacent to each other, and said lower intermediate portion has an arithmetic mean of roughness profile about one-tenth that of said adjacent hozzle end, and said upper intermediate portion has an arithmetic mean of roughness profile greater than that of said lower intermediate portion and less them that of said hozzle end.
 4. In a golf club shaft having a hozzle end and a tip adjacent thereto for insertion into a golf club hozzle, the improvement wherein said hozzle end has an outer surface that is covered with a textured surface coating having an arithmetic mean of profile roughness of greater than about 0.5 microns.
 5. A golf club shaft according to claim 4 wherein said arithmetic mean of profile roughness at said hozzle end is between about 4.3 microns and about 5.0 microns over a length of between about five centimeters and about fifty centimeters.
 6. A golf club shaft according to claim 4 further comprising a lower intermediate portion adjacent said hozzle end between about ten centimeters and about fifty centimeters in length and having an outer surface with an arithmetic mean of roughness profile of between about 0.43 microns and about 0.50 microns.
 7. A golf club shaft according to claim 6 further comprising an upper intermediate portion adjacent said lower intermediate portion between about ten centimeters and about fifty centimeters in length and having an outer surface with an arithmetic mean of roughness profile of between about 0.80 microns and about 0.90 microns.
 8. In a golf club shaft which has a hozzle end terminating in a tip, an opposite butt end, and a shank that tapers from a smallest diameter at said hozzle end to a largest diameter at said butt end, the improvement wherein at least a portion of the outer surface of said shank has a granulated surface texture thereon defining peaks with valleys therebetween, and said serviced texture has an arithmetic mean of profile roughness as measured between said peaks and valleys of at least about 0.50 microns.
 9. A golf club shaft according to claim 8 wherein said profile roughness at said hozzle end adjacent said tip is at least about four microns and said profile roughness elsewhere on said surface of said shank is less than one micron.
 10. A golf club shaft according to claim 9 wherein said hozzle end of said outer surface of said shank has a roughness profile of between about 4.3 microns and about 5.0 microns.
 11. A golf club shaft according to claim 9 wherein said hozzle end of said shaft has a granulated surface with a roughness profile of between about 4.3 microns and about 5.0 microns over a length extending a distance of at least five centimeters from said tip.
 12. A golf club shaft according to claim 11 wherein said hozzle end of said shaft has a granulated surface as aforesaid up to a maximum distance of about fifty centimeters from said tip.
 13. A golf club shaft according to claim 8 wherein said golf club shaft shank has a lower intermediate portion and an upper intermediate portion located longitudinally adjacent said lower intermediate portion and said lower intermediate portion is located longitudinally between said hozzle end of said shank and said upper intermediate portion thereof, and said upper intermediate portion is located longitudinally between said lower intermediate portion and said butt end of said shank, and said surface of said shank at said lower intermediate portion is granulated with a service texture having an arithmetic mean of profile roughness about one-tenth that of said hozzle end.
 14. A golf club shaft according to claim 13 wherein said surface of said shank at said upper intermediate portion is granulated with a surface texture having an arithmetic mean of profile roughness greater than that of said lower intermediate portion and less than that of said hozzle end.
 15. A golf club shaft according to claim 14 wherein said surface of said shank is granulated with an arithmetic mean of profile roughness of between about 4.3 microns and about 5.0 microns at said hozzle end, between about 0.43 microns and about 0.50 microns at said lower intermediate portion, and between about 0.80 microns and about 0.90 microns at said upper intermediate portion.
 16. A golf club shaft according to claim 13 wherein said arithmetic means of profile roughness are between about 4.3 microns and about 5.0 microns at said hozzle end; between about 0.43 microns and about 0.50 microns at said lower intermediate portion; and between about 0.80 microns and about 0.90 microns at said upper intermediate portion.
 17. A golf club shaft according to claim 16 wherein said hozzle end of said shank is between about five centimeters and about fifty centimeters in length, said lower intermediate portion is between about ten centimeters and about fifty centimeters in length, said upper intermediate portion is between about ten centimeters and about fifty centimeters in length, and said butt end of portion is between about fifteen centimeters and about forty centimeters in length. 